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Abstract:

Method for controlling regeneration within an after-treatment component
of an engine comprises receiving an upstream temperature signal,
receiving a downstream temperature signal, and calculating a temperature
difference based on a difference between the upstream temperature signal
and the downstream temperature signal. The temperature difference is
compared to a predetermined temperature change limit to determine whether
the temperature difference is less than or greater than the predetermined
temperature change limit. If the temperature difference is less than the
predetermined temperature change limit, an estimate of accumulated
particulate matter in the after-treatment component is calculated using a
primary soot accumulation model. If the temperature difference is greater
than the predetermined temperature change limit, an estimate of
accumulated particulate matter in the after-treatment component is
calculated using a secondary soot accumulation model. The estimate of
accumulated particulate matter in the after-treatment component is
compared to a predetermined threshold associated with the after-treatment
component.

Claims:

1. A method for controlling regeneration within an after-treatment
component of an engine, comprising: receiving an upstream temperature
signal representing a temperature of an exhaust stream upstream from the
after-treatment component; receiving a downstream temperature signal
representing a temperature of the exhaust stream downstream from the
after-treatment component; calculating a temperature difference across
the after-treatment component based on a difference between the upstream
temperature signal and the downstream temperature signal; comparing the
temperature difference across the after-treatment component to a
predetermined temperature change limit to determine whether the
temperature difference across the after-treatment component is less than
or greater than the predetermined temperature change limit; if the
temperature difference across the after-treatment component is less than
the predetermined temperature change limit, calculating an estimate of
accumulated particulate matter in the after-treatment component using a
primary soot accumulation model, and if the temperature difference across
the after-treatment component is greater than the predetermined
temperature change limit, calculating an estimate of accumulated
particulate matter in the after-treatment component using a secondary
soot accumulation model; comparing the estimate of accumulated
particulate matter in the after-treatment component to a predetermined
threshold associated with the after-treatment component; and initiating a
remedial action when the estimate of accumulated particulate matter in
the after-treatment component exceeds the predetermined threshold.

2. The method of claim 1, wherein the primary soot accumulation model is
based on a pressure decrease index indicative of a decrease in pressure
of an exhaust stream as it passes through the after-treatment component.

3. The method of claim 1, wherein the primary soot accumulation model is
based on a flow rate index indicative of a rate of flow of the exhaust
stream.

4. The method of claim 1, wherein the primary soot accumulation model is
based on a relationship between a pressure decrease index indicative of a
decrease in pressure of an exhaust stream as it passes through the
after-treatment component and a flow rate index indicative of a rate of
flow of the exhaust stream.

5. The method of claim 1, wherein the secondary soot accumulation model
is based on a soot rate map developed using an engine-out condition.

6. The method of claim 2, wherein the pressure decrease index represents
a pressure ratio across the after-treatment component.

7. The method of claim 3, wherein the flow rate index is based on a speed
of the engine.

8. The method of claim 1, wherein initiating a remedial action comprises
adjusting one or more engine control parameters so as to modify operation
of the engine to promote passive regeneration in the after-treatment
component.

9. The method of claim 8, wherein said adjusting is configured to provide
a minimum temperature at the after-treatment component to promote
regeneration in the after-treatment component.

10. The method of claim 8, wherein said adjusting comprises modifying
fueling and timing of the engine.

11. The method of claim 1, wherein said remedial action comprises
activating an auxiliary heating element to increase a temperature of the
exhaust stream.

12. The method of claim 8, wherein the remedial action comprises
activating a warning light instructing an operator to initiate
regeneration in the after-treatment component.

13. A system for controlling regeneration within an after-treatment
component of an engine comprising: a regeneration controller having a
processor coupled to a memory storage device, the regeneration controller
being configured to: receive an upstream temperature signal representing
a temperature of an exhaust stream upstream from the after-treatment
component; receive a downstream temperature signal representing a
temperature of the exhaust stream downstream from the after-treatment
component; calculate a temperature difference across the after-treatment
component based on a difference between the upstream temperature signal
and the downstream temperature signal; compare the temperature difference
across the after-treatment component to a predetermined temperature
change limit to determine whether the temperature difference across the
after-treatment component is less than or greater than the predetermined
temperature change limit; calculate an estimate of accumulated
particulate matter in the after-treatment component using a primary soot
accumulation model if the temperature difference across the
after-treatment component is less than the predetermined temperature
change limit; calculate an estimate of accumulated particulate matter in
the after-treatment component using a secondary soot accumulation model
if the temperature difference across the after-treatment component is
greater than the predetermined temperature change limit; compare the
estimate of accumulated particulate matter in the after-treatment
component to a predetermined threshold associated with the
after-treatment component; and initiate a remedial action when the
estimate of accumulated particulate matter in the after-treatment
component exceeds the predetermined threshold.

14. The system of claim 13, wherein the primary soot accumulation model
is based on a pressure decrease index indicative of a decrease in
pressure of an exhaust stream as it passes through the after-treatment
component.

15. The system of claim 13, wherein the primary soot accumulation model
is based on a flow rate index indicative of a rate of flow of the exhaust
stream.

16. The system of claim 13, wherein the primary soot accumulation model
is based on a relationship between a pressure decrease index indicative
of a decrease in pressure of an exhaust stream as it passes through the
after-treatment component and a flow rate index indicative of a rate of
flow of the exhaust stream.

17. The system of claim 13, wherein the secondary soot accumulation model
is based on a soot rate map developed using an engine-out condition.

18. The system of claim 14, wherein the pressure decrease index
represents a pressure ratio across the after-treatment component.

19. The system of claim 15, wherein the flow rate index is based on a
speed of the engine.

20. The system of claim 13, wherein initiating a remedial action
comprises adjusting one or more engine control parameters so as to modify
operation of the engine to promote passive regeneration in the
after-treatment component.

Description:

FIELD OF THE INVENTION

[0001] The subject invention relates to after-treatment systems for
compression-ignition engines and more particularly to a system and method
for controlling regeneration within an after-treatment component of a
compression-ignition engine.

BACKGROUND

[0002] The emission of particulate matter in exhaust from
compression-ignition engines is regulated for environmental reasons.
Thus, vehicles equipped with compression-ignition engines often include
after-treatment components such as particulate filters, catalyzed soot
filters and adsorption catalysts for removing particulate matter and
other regulated constituents (e.g., nitrogen oxides or NOx) from their
exhaust streams. Particulate filters and other after-treatment components
can be effective, but can also increase back pressure as they collect
particulate matter.

[0003] Particulate matter may include ash and unburned carbon particles
generally referred to as soot. As this carbon-based particulate matter
accumulates in the after-treatment components, it can increase back
pressure in the exhaust system. Engines that have large rates of
particulate mass emission can develop excessive back pressure levels in a
relatively short period of time, decreasing engine efficiency and power
producing capacity. Therefore, it is desired to have particulate
filtration systems that minimize back-pressure while effectively
capturing particulate matter in the exhaust.

[0004] To accomplish both of these competing goals, after-treatment
components must be regularly monitored and maintained either by replacing
components or by removing the accumulated soot. Cleaning the accumulated
soot from an after-treatment component can be achieved via oxidation to
CO2 (i.e., burning-off) and is known in the art as regeneration. To avoid
service interruptions, regeneration is generally preferred over
replacement of after-treatment components.

[0005] One way that regeneration may be accomplished is by increasing the
temperatures of the filter material and/or the collected particulate
matter to levels above the combustion temperature of the particulate
matter. Elevating the temperature facilitates consumption of the soot by
allowing the excess oxygen in the exhaust gas to oxidize the particulate
matter. Particulate matter may also be oxidized, and thus removed, at
lower temperatures by exposing the particulate matter to sufficient
concentrations of nitrogen dioxide (NO2). Exhaust from a
compression-engine, such as a diesel engine, typically contains NOx,
which consists primarily of nitric oxide (NO) and approximately 5 to 20
percent NO2, with greater levels of NO2 being common where oxidation
catalysts are present in the exhaust stream. Thus, some level of
regeneration occurs even at relatively low temperatures.

[0006] The regeneration process can be either passive or active. In
passive systems, regeneration occurs whenever heat (e.g., carried by the
exhaust gasses) and soot (e.g., trapped in the after-treatment
components) are sufficient to facilitate oxidation, and/or whenever
sufficient concentrations of NO2 are present in the exhaust to enable
oxidation at lower temperatures. In active systems, regeneration is
induced at desired times by introducing heat from an outside source
(e.g., an electrical heater, a fuel burner, a microwave heater, and/or
from the engine itself, such as with a late in-cylinder injection or
injection of fuel directly into the exhaust stream). Active regeneration
can be initiated during various vehicle operations and exhaust
conditions. Among these favorable operating conditions are stationary
vehicle operations such as when the vehicle is at rest, for example,
during a refueling stop. Engine control systems can be used to predict
when it may be advantageous to actively facilitate a regeneration event
and to effectuate control over the regeneration process.

[0007] An engine control system may use a soot model to deduce (i.e.,
predict) a mass of soot accumulated in the after-treatment component by
monitoring properties of the exhaust stream as it flows through the
after-treatment component. The control system can use the deduced soot
mass data to monitor soot loading over time, to determine or anticipate
when regeneration may be necessary or desirable, to facilitate a
regeneration event, and/or to effectuate control over a regeneration
process or other remedial measures. In one exemplary soot model, the
pressure decrease across a loaded after-treatment component may be used,
along with knowledge of the relationship between soot accumulation and
pressure decrease, to estimate the extent of soot loading in the
after-treatment component. This is possible because, as soot accumulates
in an after-treatment component, the pressure decrease typically
increases (at specific temperature and volumetric flow rates) from
pressure decreases experienced when the after-treatment component is
clean.

[0008] Because changes in temperature, pressure, and flow rate affect the
pressure decrease experienced by exhaust as it passes through an
after-treatment component, the accuracy and reliability of measurements
for these parameters is important. Ideal gas laws may also be used to
adjust flow rates for changing temperatures and pressures, further adding
to the importance of accurate determinations for these parameters.
Unfortunately, however, a number of difficulties have been encountered
determining temperatures in and around after-treatment components. For
example, experience has shown that exhaust gas temperatures can deviate
significantly from material temperatures in an after-treatment component,
particularly during non-steady, or transient, operation. This is due to
significant thermal inertias that may exist in typical after-treatment
components, which can be accompanied by correspondingly large temperature
gradients as the components respond to transient operating conditions.
Therefore, as a result of the large dependency on an accurate temperature
measurement, errors can be caused by temperature gradients occurring in
after-treatment components.

[0009] Accordingly, it is desirable to provide an improved system and
method for determining when to facilitate active regeneration and for
controlling active regeneration of particulate filtration systems,
particularly having improved model accuracy in the presence of large
temperature gradients occurring in and around after-treatment components.

SUMMARY OF THE INVENTION

[0010] In one exemplary embodiment of the invention, a method for
controlling regeneration within an after-treatment component of an engine
comprises receiving an upstream temperature signal representing a
temperature upstream from the after-treatment component, receiving a
downstream temperature signal representing a temperature downstream from
the after-treatment component, and calculating a temperature difference
across the after-treatment component based on a difference between the
upstream temperature signal and the downstream temperature signal. The
temperature difference across the after-treatment component is compared
to a predetermined temperature change limit to determine whether the
temperature difference across the after-treatment component is less than
or greater than the predetermined temperature change limit.

[0011] If the temperature difference across the after-treatment component
is less than the predetermined temperature change limit, an estimate of
accumulated particulate matter in the after-treatment component is
calculated using a primary soot accumulation model. If the temperature
difference across the after-treatment component is greater than the
predetermined temperature change limit, an estimate of accumulated
particulate matter in the after-treatment component is calculated using a
secondary soot accumulation model. The estimate of accumulated
particulate matter in the after-treatment component is compared to a
predetermined threshold associated with the after-treatment component,
and a remedial action is initiated when the estimate of accumulated
particulate matter in the after-treatment component exceeds the
predetermined threshold.

[0012] In another exemplary embodiment of the invention, a system for
controlling regeneration within an after-treatment component comprises a
regeneration controller having a processor coupled to a memory storage
device. The regeneration controller is configured to receive an upstream
temperature signal representing a temperature upstream from the
after-treatment component, to receive a downstream temperature signal
representing a temperature downstream from the after-treatment component,
and to calculate a temperature difference across the after-treatment
component based on a difference between the upstream temperature signal
and the downstream temperature signal.

[0013] The regeneration controller is also configured to compare the
temperature difference across the after-treatment component to a
predetermined temperature change limit to determine whether the
temperature difference across the after-treatment component is less than
or greater than the predetermined temperature change limit, to calculate
an estimate of accumulated particulate matter in the after-treatment
component using a primary soot accumulation model if the temperature
difference across the after-treatment component is less than the
predetermined temperature change limit, and to calculate an estimate of
accumulated particulate matter in the after-treatment component using a
secondary soot accumulation model if the temperature difference across
the after-treatment component is greater than the predetermined
temperature change limit. The regeneration controller is also configured
to compare the estimate of accumulated particulate matter in the
after-treatment component to a predetermined threshold associated with
the after-treatment component and to initiate a remedial action when the
estimate of accumulated particulate matter in the after-treatment
component exceeds the predetermined threshold.

[0014] The above features and advantages and other features and advantages
of the invention are readily apparent from the following detailed
description of the invention when taken in connection with the
accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Other features, advantages and details appear, by way of example
only, in the following detailed description of embodiments, the detailed
description referring to the drawings in which:

[0016] FIG. 1 is a schematic diagram showing an exemplary system for
controlling regeneration within an after-treatment component of a
compression-ignition engine, and

[0017] FIG. 2 is a process flow diagram showing an exemplary process for
controlling regeneration within an after-treatment component of a
compression-ignition engine.

DESCRIPTION OF THE EMBODIMENTS

[0018] The following description is merely exemplary in nature and is not
intended to limit the present disclosure, its application or uses. It
should be understood that throughout the drawings, corresponding
reference numerals indicate like or corresponding parts and features.

[0019] In accordance with an exemplary embodiment of the invention, as
shown in FIG. 1, an exemplary system 100 for controlling regeneration
within an after-treatment component of a compression-ignition engine
includes a compression-ignition engine 102 coupled to an exhaust system
104, through which exhaust 103 from engine 102 passes and is treated
before being discharged to the atmosphere. Exhaust system 104 includes at
least one after-treatment component 106 such as a particulate filter for
removing particulate matter and other regulated constituents from the
exhaust stream. A heater 108 is configured for adding heat to the
after-treatment component 106 to induce regeneration in the
after-treatment component 106. A regeneration controller 110 is
configured to predict when it may be necessary or advantageous to undergo
regeneration in the after-treatment component and, when appropriate, to
actively facilitate a regeneration event. The regeneration controller 110
may facilitate such an event, for example, by introducing heat to the
after-treatment component 106 from an outside source such as the heater
108 or by causing injection of fuel into the engine 102 or the exhaust
system 104.

[0020] To enable the regeneration controller 110 to better perform its
functions, various instruments are positioned within the engine 102 and
the exhaust system 104. The instruments are configured to be responsive
to changes in relevant parameters in the engine 102 and the exhaust
system 104 and to transmit signals to the regeneration controller 110
with the signals being indicative of operation of the engine 102 and the
after-treatment component 106. For example, in an exemplary embodiment,
an upstream pressure sensor 112 measures pressures of the exhaust stream
103 upstream from the after-treatment component 106 and produces upstream
pressure signals 114. Similarly, a downstream pressure sensor 116
measures pressures of the exhaust stream 103 downstream from the
after-treatment component 106 and produces downstream pressure signals
118. In addition, an upstream temperature sensor 120 measures
temperatures of the exhaust stream 103 upstream from the after-treatment
component 106 and produces upstream temperature signals 122. A downstream
temperature sensor 124 measures temperatures of the exhaust stream
downstream from the after-treatment component 106 and produces downstream
temperature signals 126. An engine speed sensor 128 senses speeds of the
engine 102 and produces engine speed signals 130. An engine flow sensor
132 senses mass flow rates of working fluid (e.g., air or air and fuel or
exhaust gas) flowing in the engine 102 or exhaust system 104 and produces
engine flow rate signals 134.

[0021] The regeneration controller 110 receives information, such as one
or more of the upstream pressure signals 114, downstream pressure signals
118, upstream temperature signals 122, downstream temperature signals
126, engine speed signals 130, and engine flow rate signals 134 from the
upstream pressure sensor 112, the downstream pressure sensor 116, the
upstream temperature sensor 120, the downstream temperature sensor 124,
the engine speed sensor 128, and the engine flow sensor 132. A processor
136 of the regeneration controller 110 cooperates with a memory 138
associated with the regeneration controller 110 to execute instructions
that are configured to enable the regeneration controller 110 to monitor
soot loading in the after-treatment component 106, to determine or
anticipate when regeneration in the after-treatment component 106 may be
necessary or desirable, to facilitate a regeneration event in the
after-treatment component 106, and/or to effectuate control over a
regeneration process or other remedial measures.

[0022] For example, in an exemplary embodiment, a regeneration controller
110 is configured to estimate a quantity of particulate matter
accumulation in the after-treatment component 106 based on a pressure
decrease index that is indicative of a decrease in pressure of the
exhaust stream as it passes through the after-treatment component 106. In
an exemplary embodiment, the regeneration controller 110 uses the
upstream pressure signals 114 and the downstream pressure signals 118 to
compute the pressure decrease index. In addition, the regeneration
controller 110 uses the engine flow rate signals 134 or the engine speed
signals from the engine speed sensor 128 or the engine flow sensor 132 to
generate a flow rate index. Still further, the regeneration controller
110 uses the upstream temperature signals 122 and the downstream
temperature signals 126 to compute a temperature index indicative of a
temperature of the exhaust stream 103 or of a change in temperature of
the exhaust stream as it passes through the after-treatment component
106. In situations where one or more of the temperature signals (e.g.,
one of the upstream temperature signals 122 and the downstream
temperature signals 126) do not exist or are deemed unreliable, or in
situations where greater detail in terms of temperatures within the
after-treatment component 106 may be desired, a simulation model may be
used to estimate one or more temperatures at one or more locations within
the after-treatment component based on other known temperatures. Then,
based on the additional temperature detail, a more accurate temperature
index may be generated.

[0023] Once the properties of the flow stream have been generated, the
regeneration controller 110 estimates a quantity of particulate matter
accumulation in the after-treatment component 106. In an exemplary
embodiment, the regeneration controller 110 uses a soot accumulation
model based on soot rate maps developed using engine-out conditions. In
another exemplary embodiment, the regeneration controller 110 uses a soot
accumulation model based on the relationship between the pressure
decrease index, the flow rate index, and the temperature index. As one
skilled in the art will appreciate, increases in the amount of pressure
decrease (i.e., change) at a constant flow rate and temperature is
indicative of accumulation of soot or other particulate matter in the
after-treatment component 106. Those skilled in the art will also
appreciate that the flow rate index may be normalized to a standardized
temperature and a standardized pressure (e.g., according to the ideal gas
law) so as to eliminate some or all of the inaccuracies associated with
changes in temperature and pressure of the exhaust stream 103. This is
possible because it is known that a consistent relationship may exist
between pressure loss and such a corrected flow rate even though
temperature and/or pressure of the flow may change.

[0024] It has been recognized that the existence of some extreme or
non-steady or transient conditions in the exhaust stream 103 and/or in
the after-treatment component 106 may result in inaccuracies in the
determination of temperature or other relevant parameters. Therefore, in
an exemplary embodiment, the regeneration controller 110 determines
whether to rely upon a primary soot accumulation model, such as a
pressure-based soot model, or a secondary soot accumulation model or
another back-up technique. The decision which technique to use may be
based on the temperature measured upstream from the after-treatment
component, and temperature measured downstream from the after-treatment
component, and a modeled surface temperature within the after-treatment
component. For example, when the temperature measured upstream from the
after-treatment component exceeds a predetermined threshold, the
regeneration controller 110 may choose to rely upon an alternative soot
estimation technique rather that using a pressure-based prediction method
that may be unreliable at the excessively high temperature. In an
exemplary embodiment, an alternative soot estimation technique relies
upon a soot accumulation model that is based on soot rate maps developed
based on engine-out conditions. At such conditions, the regeneration
controller 110 may also disable the pressure-based soot model so as to
avoid generating or using an unreliable estimate of soot accumulation.
The regeneration controller 110 may choose to rely upon an alternative
soot estimation technique whenever the temperature difference (or
gradient) across the after-treatment component exceeds a predetermined
threshold. In accordance with such embodiments, the regeneration
controller 110 may facilitate the setting and adjustment of limits on the
temperature gradient and rate of temperature change, above which the
pressure-based soot accumulation model is not executed or relied upon for
soot estimation.

[0025] It should be appreciated that a number of expressions exist for
quantifying and tracking pressure decrease in an after-treatment
component. For example, in one embodiment, the pressure decrease index is
calculated as a ratio of upstream pressure to downstream pressure (i.e.,
PR=Pu/Pd) so as to represent a pressure ratio across the after-treatment
component. In another embodiment, the pressure decrease index is
calculated as a difference between the upstream pressure and the
downstream pressure (i.e., DP=Pu-Pd) so as to represent a difference in
pressure across the after-treatment component. In still another
embodiment, the pressure decrease index is calculated as the difference
between the upstream pressure and the downstream pressure, with the
difference divided by the magnitude of the upstream pressure (i.e., as a
normalized pressure decrease, DPP=DP/Pu) so as to represent a normalized
difference in pressure across the after-treatment component. As those
skilled in the art will appreciate, the above-described flow rate index
signal can be produced by an engine speed sensor or a mass airflow sensor
or any other sensor configured to sense an engine operating condition
that is indicative of the relative flow rate of the exhaust stream 103.

[0026] In addition, the regeneration controller 110 is configured to
determine a rate of change of any of the above-described parameters. For
example, a rate of change may be calculated by capturing a first signal
associated with a first parameter (e.g., one of the upstream pressure
signals 114, downstream pressure signals 118, upstream temperature
signals 122, downstream temperature signals 126, engine speed signals
130, engine flow rate signals 134, or one of the indexes described above)
at a first time, and capturing a second reading associated with that same
parameter at a second time, wherein the second time occurs an incremental
amount of time after the first time. Then, the regeneration controller
110 may determine a change in the readings associated with the first
parameter by calculating a difference between the second reading and the
first reading. From that change, the regeneration controller 110 may
determine a rate of change in the readings associated with the first
parameter.

[0027] When a pressure-based soot accumulation model is to be executed or
relied upon for soot estimation, the regeneration controller 110 may
estimate the accumulated particulate matter in the after-treatment
component based, at least in part, on a soot accumulation model. As
described above, the model may require knowledge of the pressures,
temperatures, and flow rates of the exhaust stream 103 as described
above. In an exemplary embodiment, the estimate produced by the model
represents the amount of particulate matter that is predicted to have
accumulated in the after-treatment component. The pressure-based soot
accumulation model, which may be based on empirical data, is configured
to reflect the relationship between the amount of particulate matter that
has accumulated in the after-treatment component, the pressure decrease
index, the flow index, and the temperature index.

[0028] Since the estimate of matter accumulated in the after-treatment
component is to be compared to a predetermined threshold associated with
the after-treatment component, and since a remedial action may be
facilitated when the adjusted estimate of accumulated particulate matter
in the after-treatment component exceeds the predetermined threshold,
inaccuracies in the process would have the potential to trigger
regeneration processes unnecessarily or late. Therefore, by relying upon
an alternative soot estimation technique whenever the temperature
difference (or gradient) across the after-treatment component exceeds a
predetermined threshold, the regeneration controller 110 may improve
reliability of the estimated level of soot accumulation, thereby reducing
the need for excessive margins and potentially eliminating unnecessary
service.

[0029] In accordance with an exemplary embodiment of the invention, as
shown in FIG. 2, an exemplary process 200 for controlling regeneration
within an after-treatment component of a compression-ignition engine,
such as a particulate filter, generally includes the step of receiving
one or more values of one or more parameters associated with an exhaust
stream passing through the after-treatment component (step 210). In an
exemplary embodiment, the parameter may represent upstream pressure,
downstream pressure, upstream temperature, downstream temperature, engine
speed, or engine flow rate. The value may be received as a signal from
the upstream pressure sensor 112, the downstream pressure sensor 116, the
upstream temperature sensor 120, the downstream temperature sensor 124,
the engine speed sensor 128, and the engine flow sensor 132. The
parameter may be a pressure decrease index indicative of a decrease in
pressure of an exhaust stream 103 as it passes through the
after-treatment component 106, a flow rate index indicative of a rate of
flow of the exhaust stream, or a temperature index indicative of a
temperature of the exhaust stream.

[0030] In addition to receiving one or more values, the process 200
includes evaluating whether a temperature measured upstream from the
after-treatment component exceeds a predetermined threshold (step 220).
More specifically, this step of the process includes: (a) receiving an
upstream temperature signal representing a temperature upstream from the
after-treatment component (step 222); (b) receiving a downstream
temperature signal representing a temperature downstream from the
after-treatment component (step 224); (c) calculating a temperature
difference across the after-treatment component based on a difference
between the upstream temperature signal and the downstream temperature
signal (step 226); and (d) comparing the temperature difference across
the after-treatment component to a predetermined temperature change limit
to determine whether the temperature difference across the
after-treatment component is less than or greater than the predetermined
temperature change limit (step 228).

[0031] When the temperature measured upstream from the after-treatment
component does in fact exceed a predetermined threshold, the regeneration
controller 110 chooses to rely upon an alternative (i.e., secondary) soot
estimation technique rather than using a pressure-based prediction method
that may be unreliable at the excessively high temperature (step 230). As
discussed above, in an exemplary embodiment, the regeneration controller
110 may rely upon a soot accumulation model that is based on soot rate
maps developed based on engine-out conditions (step 232). To facilitate
use of an alternative model or technique, it may be necessary for the
regeneration controller 110 to acquire additional parameters (step 234).
In addition, the regeneration controller 110 may disable the
pressure-based soot model (step 236) so as to avoid generating or using
an unreliable estimate of soot accumulation. Still further, the
regeneration controller 110 may facilitate the setting and adjustment of
limits on the temperature gradient and rate of temperature change, above
which the pressure-based soot accumulation model is not executed or
relied upon for soot estimation (step 240).

[0032] When the temperature measured upstream from the after-treatment
component does not exceed the predetermined threshold, the regeneration
controller 110 may rely upon a primary soot estimation technique, such as
a soot accumulation model based on pressure decrease, to calculate an
estimate of accumulated particulate matter in the after-treatment
component (step 250). In one embodiment, this calculation is based, at
least in part, on a soot accumulation model and the values for pressure
decrease index, flow rate index, and temperature index. The estimate of
accumulated particulate matter in the after-treatment component is then
compared to one or more predetermined thresholds associated with the
after-treatment component (step 260). A remedial action is initiated when
the adjusted estimate of accumulated particulate matter in the
after-treatment component exceeds the predetermined threshold (step 270).

[0033] In an exemplary embodiment, and according to a primary estimation
technique, the step of estimating the quantity of accumulated particulate
matter in the after-treatment component (step 250) begins with the
calculation or receipt of a pressure decrease index indicative of a
decrease in pressure of an exhaust stream as it passes through the
after-treatment component (step 252). In an exemplary embodiment, the
pressure decrease index is indicative of the level of pressure decrease
experienced by the exhaust stream 103 as it passes through the
after-treatment component 106. In one embodiment, the pressure decrease
index is calculated as a ratio of upstream to downstream pressure (i.e.,
PR=Pu/Pd) so as to represent a pressure ratio across the after-treatment
component.

[0034] In another embodiment, the pressure decrease index is calculated as
a difference between the upstream and downstream pressures (i.e.,
DP=Pu-Pd) so as to represent a difference in pressure across the
after-treatment component. In still another embodiment, the pressure
decrease index is calculated as the difference between the upstream and
downstream pressures divided by the magnitude of the upstream pressure
(i.e., as a normalized pressure decrease, DPP=DP/Pu) so as to represent a
normalized difference in pressure across the after-treatment component.
An exemplary step of estimating the quantity of accumulated particulate
matter in the after-treatment component (step 250) also includes
determining a flow rate index that is indicative of a relative flow rate
of the exhaust stream (step 254). The flow rate index signal can be
produced by an engine speed sensor or a mass airflow sensor or any other
sensor configured to sense an engine operating condition that is
indicative of the relative flow rate of the exhaust stream.

[0035] Once the pressure decrease index and the flow index of the exhaust
stream 103 have been determined, an exemplary step of estimating the
quantity of accumulated particulate matter in the after-treatment
component (step 250) employs a pressure-based soot accumulation model
(step 256) to estimate the accumulated particulate matter in the
after-treatment component based on the pressure decrease index and the
flow rate index. As discussed above, however, when the temperature
measured upstream from the after-treatment component exceeds a
predetermined threshold, the regeneration controller 110 may choose to
rely upon an alternative soot estimation technique rather that using a
pressure-based prediction method that may be unreliable at the
excessively high temperatures (step 230). As discussed above, in an
exemplary embodiment, when temperatures exceed the threshold, the
regeneration controller 110 relies upon a soot accumulation model that is
based on soot rate maps developed based on engine-out conditions (step
232).

[0036] Regardless of which technique is used, an estimate is produced
representing an amount of particulate matter that is predicted to have
accumulated in the after-treatment component. The pressure-based soot
accumulation model, which may be based on empirical data, is configured
to reflect the relationship between the amount of particulate matter that
has accumulated in the after-treatment component, the pressure decrease
index, and the flow index. Other techniques may reflect other
relationships and may be similarly correlated to observed data.

[0037] In an exemplary embodiment, the step of initiating a remedial
action (step 270) comprises adjusting one or more engine control
parameters so as to modify operation of the engine to promote passive
regeneration in the after-treatment component (step 272). For example,
the one or more adjustments may be configured to provide a minimum
temperature at the after-treatment component 106 promoting passive
regeneration in the after-treatment component. Alternatively the one or
more adjustments may comprise modifying fueling and timing of the engine
(step 274) or activating an auxiliary heating element 108 to increase a
temperature of the exhaust stream (step 276) or activating a warning
light instructing the operator to initiate regeneration in (or
replacement of) the after-treatment component (step 278).

[0038] While the invention has been described with reference to exemplary
embodiments, it will be understood by those skilled in the art that
various changes may be made and equivalents may be substituted for
elements thereof without departing from the scope of the invention. In
addition, many modifications may be made to adapt a particular situation
or material to the teachings of the invention without departing from the
essential scope thereof. Therefore, it is intended that the invention not
be limited to the particular embodiments disclosed, but that the
invention will include all embodiments falling within the scope of the
application.